Fanno Creek Trail Embankment Stabilization

Before_redux

BEFORE

HENDERSON design-build professionals provided full assessment, permitting, and design-build services to Tualatin Hills Parks and Recreation District for the stabilization of approximately 200 feet of the Fanno Creek Trail. Fanno Creek flows approximately 15 miles from its headwaters in Portland to its confluence with the Tualatin River in Durham. Years of urban encroachment in the Fanno Creek watershed have steadily increased erosion, flooding, and pollution.

HENDERSON modeled system hydraulics to inform design and ensure that proposed conditions would produce “no rise” in flood elevations. Design alternatives were evaluated that compared the cost/benefit of moving the trail away from the creek versus moving the creek away from the trail. Ultimately, the trail would remain in place and the embankments modified.

After

AFTER

The design approach aimed to achieve stabilization of the threatened embankments using all natural materials that would add enhanced habitat function. Construction methods were chosen and continually field-adapted to minimize site impacts in and around the sensitive riparian, wetland, and upland areas. HENDERSON field crews installed approximately 50 Douglas fir logs and rootwads, 80 3-ft boulders, and 150 cubic yards of rock into two stabilization structures, strategically placing materials to divert and diffuse excessive hydraulic velocities expected within the system. Additionally, over 550 willow cuttings were integrated into the structures. The embankments were then planted by THPRD with native trees, shrubs, herbs to establish and enhance a strong riparian vegetation community and further stabilize the embankments.

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